The present invention relates to automotive fan clutches and more particularly to centrifugal force responsive clutches.
The present invention finds application for activating an automotive fan by using a plurality of internal, expanding, centrifugal acting friction shoes attached to a driven assembly. A plurality of sliding disks selectively bias a plurality of leaf springs to provide the initial torque for the friction shoes to rotate the driven assembly. The friction shoe torque capacity is designed to be greater than the torque of the driven assembly at any input driving speed causing the driven assembly to increase in speed until it reaches driving speed thus providing for a smooth engagement. The invention preferrably requires the driven assembly torque and the torque capacity of the internal shoes to follow a squared function of speed.
It is an objective of the present invention to activate a fan using a centrifugally responsive clutching mechanism. A further object of the present invention is to selectively engage and disengage a preload force on a plurality of friction shoes in cooperation with a plurality of rotating disks of differing inertia. The disks are free to rotate relative to one another by a limited amount. The rotation of the disks being controlled, in part, by a brake mechanism. Accordingly, the invention comprises: a centrifugally responsive clutch having an engaged and disengaged mode of operation comprising a driving or input member; a drum rotated by the driving member including an engagement surface and a driven member rotationally isolated from the driving member and adapted to be driven by the drum; and a brake mechanism isolated from the driving and driven members and adapted to apply a braking force to the driven member. The driven member includes a plurality of centrifugal force responsive friction shoes for drivingly engaging the engagement surface and means of generating a preload force on the friction shoes towards the engagement surface. The clutch including means for engaging and disengaging the friction shoes including a plurality to rotating disks, one of the disks rotatable with the driven member including means for causing the disks to rotate relative to one another, the relative rotation causing the engagement and disengagement of the preload on the friction shoes. Upon application of the brake the driven member slows to a stop. To disengage the driving from the driven member preferrably requires the application of a brake which has a brake torque capacity greater than the difference between the torque capacity of the friction shoes minus the driving torque .